Effect of the source of Cu on the structure and performance of Cu-Zn-Al catalysts prepared by complete liquid-phase technology
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摘要: 采用完全液相法，分别以柠檬酸铜、硝酸铜、乙酸铜为Cu源制备了三种Cu-Zn-Al浆状催化剂，考察了不同铜源对催化剂催化合成气制二甲醚性能的影响，利用XRD、H2-TPR、NH3-TPD、BET、XPS和TEM等技术对催化剂进行了表征。结果表明，铜源对催化剂织构形貌及性能影响显著，用柠檬酸铜为铜源制备的催化剂铜物种分散性最好，铜物种与其他组分间相互作用强，可还原物质的量多，同时催化剂表面弱酸量与强酸量的比较高，催化剂的甲醇脱水能力提升，三种催化剂中柠檬酸铜催化剂性能最好，CO转化率为63.4%，二甲醚选择性为66.0%。
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关键词:
- 完全液相法 /
- Cu-Zn-Al催化剂 /
- 二甲醚 /
- 柠檬酸铜 /
- 乙酸铜
Abstract: Three kinds of Cu-Zn-Al slurry catalysts were prepared respectively with copper citrate, copper nitrate and copper acetate as the source of copper by complete liquid-phase technology. The effects of different sources of copper on the catalytic performance of dimethyl ether synthesis from syngas were investigated. The catalysts were characterized by XRD, H2-TPR, NH3-TPD, BET, XPS and TEM. The results indicated that the texture morphology and catalytic performance of the catalysts varied significantly. The catalyst prepared with copper citrate showed the best dispersion of Cu species in the catalyst and the largest amount of reducable substance. Meanwhile, the Cu species have strongest interaction with other components. Copper citrate increased the ratio of the amount of weak acid and strong acid on the surface of catalysts, and also improved the performance of the catalyst for methanol dehydration. So the catalytic performance of the catalyst pre-pared with copper citrate was the best. The conversion of CO was 63.4% and the DME selectivity was 66.0%.-
Key words:
- complete liquid-phase technology /
- Cu-Zn-Al catalysts /
- dimethyl ether /
- copper citrate /
- copper acetate
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图 2 不同催化剂反应前(a)、 反应后(b)的XRD谱图
Figure 2 XRD patterns of the catalysts before (a) and after (b) reaction
图 4 反应前后催化剂氮吸附脱附等温曲线及孔径分布
Figure 4 N2-adsorption/desorption and pore size distribution curves of the catalysts
●: used catalyst; ■: fresh catalyst
图 7 催化剂反应前后的TEM照片
Figure 7 TEM imagins of the fresh and used Cat-N, Cat-Y, Cat-X catalysts
(a): Cat-N before reaction; (b): Cat-N after reaction; (c): Cat-Y before reaction; (d): Cat-Y after reaction; (e): Cat-X before reaction; (f): Cat-X after reaction
表 1 不同催化剂的活性评价
Table 1 Catalytic performance of Cat-N, Cat-X, Cat-Y
Catalyst DME yield/(mg·h-1·gcat-1) CO conversionxmol/% Selectivity smol/% DME MeOH CO2 CH Cat-N 36.84 63.39 66.03 3.97 25.94 4.06 Cat-X 29.93 55.21 61.52 2.82 30.41 5.24 Cat-Y 28.09 47.26 67.45 7.12 20.28 5.15 
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表 2 催化剂反应前后平均Cu晶粒粒径
Table 2 Copper grain size of different catalysts before and after reaction
Catalyst Cat-N Cat-X Cat-Y DCu /nm(before reaction) 20.0 19.9 25.6 DCu /nm(after reaction) 21.6 22.6 28.6 FWHM(before reaction)/(°) 0.439 0.441 0.348 FWHM(after reaction)/(°) 0.408 0.392 0.315
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表 3 催化剂反应前的H2-TPR耗氢量
Table 3 Hydrogen consumption calculated from H2-TPR
Catalyst Reduction temperature t/℃ H2 consumption w/mol Cat-N 255.4 1.634×10-3 Cat-X 245.6 1.257×10-3 Cat-Y 242.9 4.770×10-4
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表 4 不同催化剂的织构性质
Table 4 Specific surface area and pore properties of different catalysts
Catalyst Before reaction After reaction BET surface area A/(m2·g-1) pore volumev/(cm3·g-1) average pore diameter d/nm BET surface area A/(m2·g-1) pore volumev/(cm3·g-1) average pore diameter d/nm Cat-N 253.9 0.22 3.43 426.9 0.35 3.27 Cat-X 128.0 0.30 9.21 321.3 0.53 6.55 Cat-Y 392.0 0.30 3.08 457.5 0.34 2.95
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表 5 反应前催化剂的XPS和XAES数据
Table 5 XPS and XAES data of fresh catalysts
Catalyst EB/eV EK/eV α′(Cu) Cu 2p3/2 Al 2p Zn 2p3/2 Cu L3VV Zn L3M45M45 Cat-N 932.2 74.2 1 021.5 916.7 987.6 1 848.9 Cat-X 932.5 74.6 1 021.8 916.2 987.5 1 848.7 Cat-Y 932.7 73.8 1 021.4 916.3 987.9 1 849.0
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表 6 催化剂反应前表面元素物质的量比
Table 6 Mol ratios between relevant elements on fresh catalysts
Catalyst Mol ratio Cu/Zn Cu/Al (Cu+Zn)/Al Cat-N 1.28 0.08 0.14 Cat-X 1.42 0.09 0.16 Cat-Y 0.43 0.06 0.19
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